Doctor under training Jack Hazelwood has to change his plans when his family is suddenly left almost penniless. With the aid of his boss, he secures a plum post as the Medical Officer on a Nobleman's yacht as it sets out for a world cruise. Then follows a selection of the usual cataloge of adventures in any Harry Collingwood book: piracy, a lone voyage in an open boat, a damsel in distress, a paradise island, treasure, and finally, a daring stroke to set things to rights.